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RANDALLSTOWN, Md. - Police said a young man is in critical condition after he was exposed to high levels of carbon monoxide in his Randallstown home.

The young man was transported to Shock Trauma, along with his mother and brother who were treated for less severe symptoms of CO poisoning, police said in a release. Investigators believe a broken furnace may be at fault for the CO buildup.

Emergency responders were dispatched to the 8200 block of Rockdale Avenue in Randallstown at 2:32 p.m. Wednesday.

"Gas meters carried by [Baltimore County Fire Department] personnel began sounding as soon as they entered the home and detected extremely high levels of the lethal gas," the release states.

The young man was watching television in the basement when he started feeling the effects of the gas. He told his mother that he wasn't feeling well before he fell unconscious, police said.

"Firefighters' gas meters found CO levels in the home at 776 parts per million. At this level, CO can produce unconsciousness or death within a few hours," the release stated.

The home was equipped with a CO detector, although investigators said it wasn't working properly.

Stay with ABC2 News as we continue to update this story.

Copyright 2014 Scripps Media, Inc. All rights reserved. This material may not be published, broadcast, rewritten, or redistributed.